package dao.impl;

//import jdk.internal.access.JavaIOFileDescriptorAccess;
import dao. UserDao;
import pojo.User;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImpl implements UserDao {
    @Override
    public List<User> findAll() {
        //jdbc操作
        //创建集合
        List<User> users=new ArrayList<>();
        Connection connection =null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;
        //1.加载驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            //2.获取链接(url username password )
            String url="jdbc:mysql://127.0.0.1:3306/student?characterEncoding=utf-8";
            connection = DriverManager.getConnection(url, "root", "Win032917.lx");
            if(connection!=null){
                System.out.println("连接成功");
            }
            //3.写sql
            String sql="select * from student";
            //4.预编译sql
            preparedStatement = connection.prepareStatement(sql);
            //5.有参数设置参数
            //6.执行sql
            resultSet = preparedStatement.executeQuery();
            //7.遍历结果集
            while(resultSet.next()){
                User user=new User();
                user.setId(resultSet.getInt(1));
                user.setName(resultSet.getString(2));
                user.setPass(resultSet.getString(3));
                //把对象添加到集合中
                users.add(user);
            }
            //返回集合
            return users;
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally {
            //8.关闭资源
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (preparedStatement != null) {
                    preparedStatement.close();
                }
                if(connection!=null) {
                    resultSet.close();
                }
            }catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }
        //return null;
    }
}
